Pneumatic control valve for vacuum chambers

ABSTRACT

The invention concerns a differential pressure responsive valve of simple construction contained within the vacuum zone of high vacuum apparatus and operable to protect an ion pump by opening only after the pressure in a work chamber has been reduced to low level by a roughing pump.

United States Patent Ellison Aug. 29, 1972 541 PNEUMATIC CONTROL VALVE FOR [56] References Cited VACUUM CHAMBERS UNITED STATES PATENTS [72] Invent Elhmn Sherman Oaks 2,702,685 2/1955 Capsek ..25 l/6l .2 a 3,144,199 8/1964 lpsen .230/45 [73] Assignee; vaooom/Aonosphoros. Corporation, 3,446,422 5 1969 Langlais et al ..417/l99 North Hollywood, Calif. b Primary Examiner-R0 ert M. Walker [22] Wed: 1969 Attorney-White & Haefliger 21 Appl. No.: 849,100

57 ABSTRACT [52] U.S. Cl ..417/199, 251/612 The inv n n ncerns a differential pressure respon- [51] Int. Cl. ..F04b 41/06, F16k 31/145 sive valve f simpl nstruction contained within the 58 Field of Search ..340/45, 101, 69; 417/129, 205; vacuum Zone of high vacuum apparatus and Operable 251/ 12 to protect an ion pump by opening only after the pressure in a work chamber has been reduced to low level by a roughing pump.

7 Claims, 2 Drawing Figures PNEUMATIC CONTROL VALVE FOR VACUUM CHAMBERS BACKGROUND OF THE INVENTION This invention relates generally to high vacuum apparatus, and more particularly concerns the valving of such apparatus.

High vacuum systems have become increasingly useful in applications involving coating and evaporation, and for general research, engineering and production purposes. In certain of such systems it is desirable to utilize a roughing vacuum pump operable to reduce the pressure in the work chamber to low level, and an ion pump to reduce the work pressure still further. Due to the sensitivity of the ion pump, it is necessary to prevent its intake exposure to pressure in the work chamber until that pressure has been reduced to a very low level. Also, it is desirable to maintain the ion pump running at all times to eliminate the need of repumping the ion pump valve during each pumping cycle, or in the case of diffusion pumping, to eliminate the need for cooling the pump down during each pumping cycle.

In the past, the exposure of the ion pump to the work chamber was controlled as by means of a valve operated outside the work chamber. Such a valve requires precision sealing in order to prevent leakage of minute amounts of gas into the work chamber; also, reduction in size of the equipment is limited by the use of such a hand-operated valve.

SUMMARY OF THE INVENTION It is a major object of the invention to provide a differential pressure responsive valve of simple construction contained within the vacuum zone and which is operable to protect the ion pump by opening only after the pressure in the work chamber has been reduced to low level by the roughing pump. As will be seen, the valve, when closed, protects the ion pump against exposure to the work chamber, and when open the valve affords wide-mouth communication of that chamber with the ion pump for rapid evacuation of the chamber to extremely high vacuum state. Also, the valve will allow easy installation or a cryogenic shroud within the chamber and around the valve.

Basically, the invention is embodied in apparatus that comprises: a primary chamber to receive inflow of gas; first pumping and valving means connected to communicate with the chamber interior and operable to reduce the gas pressure in it to relatively low lever; second pumping and valving means connected with the chamber for reducing the gas pressure in same below that low level, the second valving means including a movable valve body controlling the outlet from the chamber; and control means including a yieldable device urging the body in a direction to open communication between the outlet and the chamber interior, and a fluid pressure responsive actuator to which control fluid pressure is communicable to urge the body in a direction to block communication between the outlet and the chamber interior during operation of the first pumping means. Typically, the yieldable device may comprise a spring which, together with the actuator, may advantageously be located within the vacuum chamber; and the control means may typically include a fluid pressure line extending from the vacuum chamber exterior to communicate with the actuator within the chamber, there being means in series with that line to control passage of control pressure to the actuator. The latter may advantageously comprise a bellows one end of which is integral with the valve body, as for example a plate, and the opposite end of the bellows may be connected to a fixed support within the vacuum chamber.

Additional objects and advantages of the invention include the connection of one end of the spring to the referred to support within the vacuum chamber, and the connection of the opposite end of the spring to a frame carried by the valve body, so as to urge the valve body toward open position. Accordingly, the bellows and spring are carried for movement in the direction of frame movement with the valve body, and guide means may be incorporated in the chamber to facilitate such movement, as will be seen.

These and other objects and advantages, as well as the details of an illustrative embodiment, will be more fully understood from the following specification and drawings, in which:

DRAWING DESCRIPTION FIG. 1 is an elevation taken in section, to show preferred form of the invention in its vacuum chamber environment; and

FIG. 2 is a fragmentary view of the valve body in open condition, together with its control.

DESCRIPTION OF PREFERRED EMBODIMENT In the drawings, the high vacuum apparatus is shown to include a primary vacuum chamber 10 to which a bell jar 11 is releasably connected at 12 to provide access to work 13 (of any desired sort) to be subjected to high vacuum treatment. The transparent jar is flanged at 14 and an annular seal 15 seals off between the flange and the top wall 10a of the chamber 10.

- A first pumping and valving means, as for example is illustrated by pump 16 and valve 17, is connected to communicate at 18 with the chamber interior 19. When the valve is open, the continuously running pump is operable to reduce the gas pressure in the chamber to relatively low (i.e. roughing) level.

In addition, a second pumping and valving means, generally indicated at 20, is connected with the chamber, via wide-mouthed port 21, for reducing the gas pressure in the chamber below the low level established by the first pump 16. The second valving means includes a movable valve body or stopper, as for example plate 22, controlling the outlet port 21 with which the second pumping means communicates. That pump may typically comprise a continuously running ion pump 23 having an inlet 24 opposite port21.

Control means, generally indicated at 25, includes a yieldable device (as for example spring 26) urging the plate 22 in the direction of arrow 27 to open communication between the outlet 21 and the chamber interior 19. The control also includes a fluid pressure responsive actuator (as for example bellows 28) to which control fluid pressure is communicable to urge the plate 22 in a direction to block off communication between the outlet 21 and the chamber interior. The latter condition is shown in FIG. 1, with the plate 22 spanning the outlet 21 and an annular seal 30 sealing off between the plate and the chamber lower wall 10b. FIG. 2, on the other hand, shows the plate lifted away from wall 10b by the spring, to open the chamber interior 19 to the ion pump inlet 24.

It will be noted that the control 25 is located in the vacuum chamber so as to obviate problems of leakage from the exterior at seals between fixed and moving parts. In this regard, the control includes a fluid pressure line 31 extending from a pressure control at 32 at the exterior to communicate via a valve 33 with the actuator 28 within the chamber. The control 32 and the valve 33 afford a means to control the passage of control fluid pressure to the actuator or bellows.

One end 34 of the bellows may be integral with the valve plate, while the opposite end 35 of the bellows is attached to the fixed support 36. The latter may have the form of a bracket, with legs 36a attached to the chamber wall 10b, and a crosspiece 36b extending parallel to the plate 22. Likewise, one end 37a of the spring is carried by the support bracket 36, while the opposite end 38 of the spring is carried by the frame member 39 spaced from the bracket and within the chamber 10. The frame 39 is in turn carried via guide rods 40 by the valve plate 22, the rods passing through guide openings 41 in the support bracket. Accordingly, movement of the plate 22 toward and away from the outlet 21 is guided by movement of rods 40 in openings 41.

' Although a vacuum pump 32 is shown for illustration purposes, the device may be designed without it. Differential pressure is all that is required in 28, with the proper force designed into spring 26. Also, by using differential pressure, the spring 26 is not required for the closing action and only the the vacuum in bellows 28 (for raising plate 22) and pressure in bellows 28 (for closing plate 22) may then be needed or used.

In operation, and before evacuation of chamber 10 and bell jar 11 work 13 is placed in the latter. Valve 17 is then opened to allow roughing pump to reduce the pressure in chamber 10 to a low level. Valve 33 is then opened, valve 42 closed and control 32 operated to reduce the pressure within the bellows sufficiently as to overcome the closing force in the spring 26 and lift the valve plate 22. Valve 17 is then closed and the ion pump allowed to operate to reduce the pressure in the chamberand bell jar to a lower level, as desired.

After elapse of the high vacuum treating interval, the chamber may be backfilled with gas as follows: valve 33 is closed and valve 42 operated to expose the inside of the bellows to atmospheric pressure so the spring may close the valve plate 22, shutting off communication of the ion pump with the chamber interior. Next, the side valve 38 in a backfill line 37 is opened to allow gas to flow into the chamber from the exterior. The bell jar 1 1 may then be removed to gain access to the work 13.

Merely as illustrative, the roughing pump may be operated to drop the pressure in the chamber to a level on the order of l X 10' torr; and the ion pump may be operated to drop the pressure still further, i.e. to a level on the order of X torr.

It will also be noted in FIG. 1 that a cryogenic baffle 60 may be introduced into the chamber interior 19, to

extend about valve and control means therefor. The latter are easily accommodated within the space inwardly of the baffle, as shown. Chamber 10 may be 1. In high vacuum apparatus, the combination comprising a. a primary chamber the interior of which is, at

times, to receive inflow of gas,

b. first pumping and valving means connected to communicate with the chamber interior and operable to reduce the gas pressure therein to relatively low level,

0. second pumping and valving means connected with the chamber interior for reducing the gas pressure therein below said low level, said second valving means including a movable valve body controlling an outlet from said chamber and with which said second pumping means communicates, and

d. control means operable to urge said body in a direction to open communication between said outlet and the chamber interior and including a fluid pressure responsive actuator to which control fluid pressure is communicable to urge said body in a direction to block communication between said outlet and the chamber interior during operation of said first means,

e. said actuator comprising a bellows one end of which is movable with the valve body, there being a fixed support for the opposite end of the bellows, and said control means comprising a spring to urge the body in a direction to open communication between said outlet and the chamber interior, and said spring, bellows and support being located within the chamber.

2. The combination of claim 1 wherein said second pumping means comprises a high vacuum pump.

3. The combination of claim 1 wherein said control means includes a fluid pressure line extending from the chamber exterior to communicate with said bellows within the chamber and means in series with said line to control the passage of control fluid pressure to said bellows.

4. The combination of claim 1 wherein one end of the spring is carried by said support, and including a frame carried by the valve body and to which force is transmitted by the opposite end of the spring.

5. The combination of claim 4 wherein said support guides movement of the frame with the valve body.

6. The combination of claim 5 wherein said support is integral with said chamber and extends interiorly thereof to guide said frame, the bellows and spring being carried for movement in the direction of the frame movement with the valve body, said body comprising a plate.

7. The combination of claim 1 including a cryogenic baffle in said chamber and extending about said actuator. 

1. In high vacuum apparatus, the combination comprising a. a primary chamber the interior of which is, at times, to receive inflow of gas, b. first pumping and valving means connected to communicate with the chamber interior and operable to reduce the gas pressure therein to relatively low level, c. second pumping and valving means connected with the chamber interior for reducing the gas pressure therein below said low level, said second valving means including a movable valve body controlling an outlet from said chamber and with which said second pumping means communicates, and d. control means operable to urge said body in a direction to open communication between said outlet and the chamber interior and including a fluid pressure responsive actuator to which control fluid pressure is communicable to urge said body in a direction to block communication between said outlet and the chamber interior during operation of said first means, e. said actuator comprising a bellows one end of which is movable with the valve body, there being a fixed support for the opposite end of the bellows, and said control means comprising a spring to urge the body in a direction to open communication between said outlet and the chamber interior, and said spring, bellows and support Being located within the chamber.
 2. The combination of claim 1 wherein said second pumping means comprises a high vacuum pump.
 3. The combination of claim 1 wherein said control means includes a fluid pressure line extending from the chamber exterior to communicate with said bellows within the chamber and means in series with said line to control the passage of control fluid pressure to said bellows.
 4. The combination of claim 1 wherein one end of the spring is carried by said support, and including a frame carried by the valve body and to which force is transmitted by the opposite end of the spring.
 5. The combination of claim 4 wherein said support guides movement of the frame with the valve body.
 6. The combination of claim 5 wherein said support is integral with said chamber and extends interiorly thereof to guide said frame, the bellows and spring being carried for movement in the direction of the frame movement with the valve body, said body comprising a plate.
 7. The combination of claim 1 including a cryogenic baffle in said chamber and extending about said actuator. 